H9N2亚型禽流感病毒对樱桃谷肉鸭的致病性

为了研究H9N2亚型禽流感病毒（AIV）对樱桃谷肉鸭的致病性。本试验利用1株鸭源H9N2亚型AIV分别通过静脉注射和鼻内接种途径感染2周龄健康樱桃谷肉鸭,观察感染鸭的症状、排毒规律及组织学变化,流式细胞术分析外周血CD4^＋和CD8^＋T细胞变化规律,实时荧光定量（RT-qPCR）检测脾脏中细胞因子的表达水平,并测定血清HI抗体效价。结果显示,攻毒后,静脉注射组鸭出现体质量增长显著缓慢、呼吸道症状以及全身性感染,而鼻内接种组鸭无明显临床症状,仅发生局部感染;两攻毒组鸭泄殖腔较气管排毒量高且排毒时间长;外周血CD8^＋T细胞显著升高,并且脾脏IFNA、IFNB、IFNG和IL2表达水平上调,IL1B和IL6表达水平仅在静脉注射组上调;血清HI抗体水平低且维持时间短。结果表明,在实验室条件下,H9N2亚型AIV对樱桃谷肉鸭致病力较弱,仅静脉接种组引起鸭体质量增长缓慢及呼吸系统出血、淋巴细胞浸润。

Experimental infection with a duck-origin H9N2 avian influenza virus in cherry valley ducks

Abstract：To investigate the outcome of H9N2 subtype avain influenza virus infection in cherry valley ducks. Cherry valley ducks at the age of two weeks were intravenously and intranasally,in- oculated with a duck-origin avian H9N2 influenza virus respectively. After infection, clinical signs, dynamics of viral shedding and histological lesions were recorded. In addition, flow cytometric analysis of CD4^＋ and CD8^＋ T-lymphocytes in peripheral blood mononuclear cells,quantitative real-time RT-PCR analysis of immune-related genes in spleen and serology test were also per- formed. After infection, adecrease in body weight gain and mild respiratory syndrome were ob- served, indicating systemic infections in intravenously inoculated ducks, however, not observed in intranasally inoculated ducks. Viral shedding presented by cloacal swabs showed a higher viral loads and longer shedding duration in infected ducks than that of tracheal swabs. By flow cytomet- tic analysis,responses of CD8^＋ T lymphocytes showed a significant increase in infected ducks. Upregulation of IFNA,IFNB,IFNG and IL2 were observed in infected ducks while upregulation of IL1B and IL6 were only recorded in intravenously infected ducks determined by quantitative re- al-time RT-PCR. Serology test showed a weak HI antibody response and shorter persistence of antibodies was observed in intravenously and intranasally infected ducks. Experimental infection with H9N2 showed low pathogenicity to cherry valley ducks, only intravenously infected ducks displayed retarded growth and evident lesions in respiratory system charactered by hemorrhage and lymphocytic infiltration